A number of systems for supporting pipes and other components from elongated, U-section components variously termed struts and channels have heretofore been proposed. Systems of the foregoing character are disclosed in U.S. Pat. Nos.: 1,668,953 issued May 8, 1928, to Erickson for MOLDING FOR ELECTRIC CABLES; U.S. Pat. No. 2,273,571 issued Feb. 17, 1942, to Hafemeister for PIPE HANGER; U.S. Pat. No. 3,042,352 issued Jul. 3, 1962, to Stamper for PIPE HANGER; U.S. Pat. No. 3,132,831 issued May 12, 1964, to Stamper for CLIP-ON PIPE HANGER; U.S. Pat. No. 3,226,069 issued Dec. 28, 1965, to Clarke for HANGER FOR CYLINDRICAL CONDUITS AND THE LIKE; U.S. Pat. No. 3,527,432 issued Sep. 8, 1970, to Lytle for PIPE OR TUBING SUPPORT; U.S. Pat. No. 3,565,385 issued Feb. 23, 1971, to Zurawski for FLUORESCENT TUBE BOX SUSPENSION SYSTEM AND MEANS; U.S. Pat. No. 3,650,499, issued Mar. 21, 1972, to Biggane for CLAMP FOR PIPE SUPPORT WITH SLANTING PIVOTAL ASSEMBLY; U.S. Pat. No. 4,417,711 issued Nov. 29, 1983, to Madej for PIPE HANGER; and U.S. Pat. No. 4,695,019 issued Sep. 22, 1987, to Lindberg et al. for NON-METALLIC STRUT SYSTEM and in: Offenlegungsschrift No. 2164991 filed 28 Dec. 1971 by Niedax Ges. F. Verlegungsmaterial mbH and laid open to public inspection on 12 Jul. 1973 and a Spring 1987 catalog from Aickinstrut, Inc., P.0. Box 569, Redmond, Wash. 98073.
Systems of the type disclosed in the foregoing patents and the Aickinstrut catalog with surface mounted struts or channels have been in use for over fifty years to support pipes, electrical raceways, and other system components form the floors, walls, and ceilings of buildings and from other structures. The struts or channels of the system are attached to the structure; and clamps, connectors, and other fittings are employed to attach the supported component (or load) to the channels or struts.
In a typical, heretofore proposed system with metal components, there is a simple frictional fit between the supporting strut or channel and the fixture installed in that channel to support a load from it (see, for example, above-cited patents U.S. Pat. Nos. 3,226,069; 3,527,432; 3,565,385; 3,650,499; and 4,417,711). With non-metallic, engineered polymers substituted for the heretofore utilized metallic components (see, as an example, above-cited U.S. Pat. No. 4,695,019), this approach proves somewhat less than satisfactory. Due to the much lower coefficients of friction, the load-supporting fixture can easily slip along the supporting strut or channel when a polymer is substituted for metal in a conventional support system design, allowing the load to shift. This is especially true in applications in which the supporting channels are vertically oriented, particularly if the load is relatively heavy or subjected to vibration or hammering and because the pipe runs are often then employed as ladder rungs. Shifting loads are of course very undesirable as they radically increase the potential for system failure.
U.S. Pat. No. 4,961,553 issued 9 Oct. 1990 to Todd for SUPPORT SYSTEMS FOR PIPES AND OTHER LOADS and copending U.S. patent application No. 07/558,581 filed 27 Jul. 1990 by Todd et al. for SUPPORT SYSTEMS AND COMPONENTS THEREOF disclose novel, improved support systems designed for the applications just described. These support systems generally include elongated struts or channels and clamps, connectors, and other fittings for attaching a load to the supporting channel. The system components may be fabricated of non-metallic materials. This makes the novel systems disclosed in the just-cited patent and application appropriate for even highly corrosive environments. At the same time, the system components are simple and relatively inexpensive to manufacture; and the resulting systems are accordingly sufficiently cost effective to be employed in even the most mundane of applications.
Perhaps most prominent among the novel features of these previously disclosed systems is the type of supporting channel which is employed. Like conventional channels, those employed in the previously disclosed systems have a U-shaped cross-section. However, there are notches in and spaced along these channels in which the load-supporting fittings can be engaged to keep the load from shifting, even in demanding applications in which the channels are vertically oriented and the loads are heavy or of a nature which causes hammering or vibration. These notches are formed in the rearmost, free or exposed edges of flanges which are integral with, and spaced inwardly from, the side walls of the channels.
One consequence of this novel construction is that the load-supporting capacity of the channel is dramatically increased. Even though the polymeric material from which it is fabricated may have lower shear strength than steel, much thicker and variable sections are practical. A second, also significant, advantage of these channels is that channel nuts and other trapped-type fittings can be employed, greatly increasing the versatility of the channel by increasing the types of fittings which may be employed with it. At the same time, and because they are fabricated from non-metallic materials, the channels under discussion can be supplied at competitive costs whereas they could not be, if fabricated from metal as previously disclosed, notched, support system channels are.
Heretofore, support systems with conventional, unnotched channels have employed metallic and non-metallic internal fittings such as channel nuts which are retained in place by friction. Particularly in systems employing non-metallic channels with their lower coefficients of friction, this approach is not without its disadvantages. Available channel nuts are relatively expensive; and large numbers of these components (typically four per foot) are required. Therefore, in a typical installation, systems employing unnotched non-metallic channels and channel nuts are not competitive unless corrosion problems are severe and support systems with metallic components can not be employed. As a corollary, such systems are typically not competitive because of the additional labor required to install them. Furthermore, even closely spaced, the channel nuts of such systems often do not provide adequate resistance to the shifting of loads in onerous applications--e.g., those involving hammering or vibrating and vertically oriented channels.
Load shifting is certainly minimized, if not eliminated, in the notched channel, non-metallic systems disclosed in the Todd patent and Todd et al. application. In these systems, positive engagement of the channel nuts in the notches of the channels keeps the channel nuts and supported loads from shifting along the channels in even the most demanding of applications. However, those Todd and Todd et al. systems employing channel nuts do have their disadvantages.
One is that they are not easily installed in a channel in that these previously disclosed channel nuts must be loaded into an end of the channel and then displaced to the wanted location. This is unwieldy if the channel is of any length and may be totally impractical if the ends of the channel are not accessible or if other load-supporting components have previously been installed between the accessible end or ends of the channel and the location where the channel nut is wanted.
Another disadvantage of the Todd and Todd et al. channel nuts is that no provision is made for retaining these channel nuts in the wanted locations while load-supporting components are being attached to them. Thus, unless the installer manually holds the channel nut in place, it is apt to slip out of the channel notches in which it is seated at the wanted location, particularly in those systems in which the channels are vertically oriented. This requirement for manual intervention by the installer slows the process of assembling the system, increasing its cost and making installers less willing to employ the system.